1. Field of the Invention
This invention relates to a hydraulic steering device of a mobile machine, such as an industrial truck. The steering device has a steering angle transmitter in a mechanically functional connection with a steering valve. As a function of the actuation of the steering angle transmitter, the steering valve controls the connection of a steering drive with a pressure fluid source and a reservoir.
Hydraulic steering devices in which a steering valve that is activated mechanically by a steering angle transmitter (such as a steering wheel, for example) controls the actuation of a steering drive (such as a steering cylinder, for example) that is functionally connected to a steered axle with the steered wheels are used in mobile machines, such as fork-lift trucks. In steering devices of this type, the steering angle sensor is in a mechanical drive connection with the steering valve by means of a steering shaft.
On steering devices of this type, the translation ratio, i.e., the number of revolutions of the steering angle sensor to actuate the steering drive from a first stop to a second stop, must be specified by the mechanically functional connection between the steering valve and the steering angle transmitter.
However, on mobile machines, in particular industrial trucks, it is desirable for the steering device to have a high translation ratio when the machine is stopped or traveling at low speed so that the steering drive can be actuated from the first stop to the second stop by means of a low number of revolutions of the steering angle transmitter. This permits the cargo-carrying capacity of the mobile machine to be increased.
At a high speed of travel of the mobile machine, it is desirable for the steering device to have a low translation ratio, i.e., a high number of revolutions of the steering angle transmitter is required to actuate the steering drive from the first stop to the second stop. AT high speeds of travel, it is thereby possible to avoid abrupt deflections of the steering drive when the steering angle sensor is activated. Thus, at high speeds of travel, the safety of the mobile machine and, in particular, the stability of the vehicle to prevent lateral tipping can be increased when the steering angle transmitter is activated.
It is an object of the invention to provide a hydrostatic steering device of the general type described above but in which the translation ratio of the steering device can be varied in a simple manner.